1. Field of the Invention
The present invention relates to a material for covering a surface of an automobile internal trim panel (hereinafter referred to as a surface material), and an automobile internal trim panel comprising the surface material. The automobile internal trim panel of the present invention can be used as, for example, a headlining, a pillar, a door trim, or a rear package.
2. Description of the Related Art
Recently, an automobile internal trim panel prepared by adhering and integrating a surface material made of an entangled nonwoven fabric and a substrate for reinforcing the surface material was developed as an automobile internal trim panel having a soft feeling and a pleasing appearance. For example, an automobile internal trim panel wherein a substrate comprises three layers of a polyurethane foam layer, a glass-fibers layer, and a backing layer; a surface material is made of a needle-punching-entangled nonwoven fabric; and the substrate and the surface material are integrated by fusion of a hot-melt film, is known. In the above automobile internal trim panel, the surface material of the needle-punching-entangled nonwoven fabric rarely becomes dirty, because of the suppression of a natural air convection within an automobile, in addition to the fusion integration by the hot-melt film. However, problems of the automobile with such an internal trim panel have been pointed out, in that the noise is loud in the inside of the automobile, and thus, the sound absorption is poor. It was found that these problems are caused by a reflection of sounds generated within the automobile room, from the hot-melt film.
Therefore, an automobile internal trim panel prepared by forming a polyurethane-based resin from a reaction of a liquid isocyanate and water, and adhering and integrating a surface material and a substrate with the polyurethane-based resin, instead of the hot-melt film, was proposed. However, in some cases, the polyurethane-based resin may permeate through the surface material to reach at the exposed surface of the surface material. The exposed surface means that the surface is exposed to the inside of the automobile. If the polyurethane-based resin reaches the exposed surface of the surface material, the exposed surface of the surface material is yellowed with time, and thus, the appearance of the room of the automobile is affected. Also there were problems in that a sufficient adhesiveness is not obtained between the surface material and the substrate, and the surface material of an automobile internal trim panel is liable to become dirty.
Further, Japanese Unexamined Patent Publication No. 61-141542 disclosed that a conjugated nonwoven fabric having a dual-layered structure of a needle-punched water-repellant nonwoven fabric sheet and a needle-punched super water absorbent nonwoven fabric sheet is used as the surface material of an automobile internal trim panel. However, the surface material of the conjugated nonwoven fabric contains super water absorbent fibers, and has an excellent water-absorption property. Therefore, it is supposed that although the reaction between liquid isocyanate and water is necessary for an adhering treatment with the substrate, the reaction is inhibited, and an adhesiveness of the surface material and the substrate is affected. In working Examples of the above Publication No. 61-141542, a needle-punched nonwoven fabric treated with a water-repellant and a needle-punched nonwoven fabric containing super water absorbent fibers are entangled with needle-punching and integrated. Although detailed procedures of the needle-punching treatment are not disclosed in the above Publication No. 61-141542, it is most probable that the needle-punching treatment was conducted onto the side of the water-repellant nonwoven fabric sheet. This is because, if the needle-punching treatment was conducted onto the side of the nonwoven fabric sheet containing the super water absorbent fibers, the super water absorbent fibers invade the water-repellant nonwoven fabric, and the water-repellency is deteriorated. When the needle-punching treatment produces prominent punched holes on the side onto which the needle-punching treatment is conducted, i.e., on the needle-punched nonwoven fabric treated with a water-repellant. Therefore, there was a defect in the surface material from a decorative point of view. Further, if an mass per unit area of the surface material is decreased to about 220 g/m2 or less to reduce the weight thereof, improve mileage, and reduce manufacturing costs, the needle-punched nonwoven fabric treated with a water-repellant is inevitably thinned, and thus, the needle-punched nonwoven fabric containing super water absorbent fibers easily becomes transparent. In general, super water absorbent fibers are white, and such a thinness will affect the decorativeness.
Further, Japanese Unexamined Patent Publication No. 5-254070 discloses an automobile internal trim panel prepared by dipping a fabric in a water-repellant solution to impregnate the inside of the fabric with the water-repellant; heating the fabric to dry; then coating the fabric with a backing agent comprising a ultraviolet-curing resin as a main ingredient on a reverse side of the fabric; and irradiating the fabric with a ultraviolet ray to solidify the backing agent. However, when the automobile internal trim panel is used as a surface material, the whole fabric forming the automobile internal trim panel contains the water-repellant, and thus, the polyurethane-based resin may permeate the internal trim panel, as shown in Comparative Example 1 in the present specification. Therefore, the exposed surface of the internal trim panel is yellowed with time, and thus, the appearance of the room of the automobile is affected.